/*
 * Copyright 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.compose.ui.draw

import androidx.compose.runtime.Stable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.graphicsLayer

/**
 * Draw content with modified alpha that may be less than 1.
 *
 * Usage of this API renders this composable into a separate graphics layer. Note when an alpha less
 * than 1.0f is provided, contents are implicitly clipped to their bounds. This is because an
 * intermediate compositing layer is created to render contents into first before being drawn into
 * the destination with the desired alpha. This layer is sized to the bounds of the composable this
 * modifier is configured on, and contents outside of these bounds are omitted.
 *
 * Performance Note: For animating alpha, it is highly recommended to use [Modifier.graphicsLayer]
 * instead (e.g., `Modifier.graphicsLayer { alpha = ... }`). Changing the `alpha` parameter on
 * `Modifier.alpha` causes the composable to be recomposed, which is less efficient than updating
 * the `alpha` property within `graphicsLayer`, as `graphicsLayer` can optimize this change without
 * requiring recomposition.
 *
 * @param alpha the fraction of children's alpha value and must be between `0` and `1`, inclusive.
 * @sample androidx.compose.ui.samples.AlphaSample
 * @see graphicsLayer
 *
 * Example usage:
 */
@Stable
fun Modifier.alpha(
    /*@FloatRange(from = 0.0, to = 1.0)*/
    alpha: Float
) = if (alpha != 1.0f) graphicsLayer(alpha = alpha, clip = true) else this
